halske



NITED STATES PATENT OFFICE.

GEORG ERLVEIN AND FRIEDRICH GUSTAV A DOLF HELLER OF BERLIN, GERMANY, ASSIGNORS TO SIEMENS & HALSKE, OF SAME PLACE.

FILAMENT FOR INCANDESCENT ELECTRIC LAMPS.

SPECIFICATION forming part of Letters Patent No. 448,914, dated March 24,1891.

Application filed July 22, 1890. Serial No. 359,545. (No specimens.)

To all whom it may concern/.-

Be it known that we, GEORG ERLWEIN, doctor of philosophy, a subject of the King of Bavaria, and FRIEDRICH GUSTAV ADOLF HELLER, a subject of the King of Saxony, both residing at Berlin, in the Kingdom of Prussia, German Empire, have invented certain new and useful Improvements in Filaments for Electric Glow-Lamps; and we do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

Our invention relates to filaments for electric glow-lamps, and has for its object the providing of a suitable filament with a shell or coating therefor to protect the said filament against disintegration from the electric current and against accidental jars and shocks tending to destroy the same.

Among the best methods for the production of a solid hardly-fusible coating or incandescent material protective against electric atomizing and the shocks of transport have proved to be the hardly-fusible metallic carbides of various hardly-fusible metals.

It has hitherto been customary to coat the filaments with deposited carbon, which being a fairly good conductor, it has been found necessary either to make the carbon filaments exceedingly fine with a sufficient protection of deposited carbon, or to make the filaments larger with an insufficient protection of deposited carbon. Both of these forms are open to grave objections, but owing to the minor conductivity of the compounds mentioned above compared with carbon the coating of them maybe made-much thicker than the coating of carbon now in general use, admitting, therefore, the use of thicker carbon cores for glow-lamps, whereby the durability of the lamp is increased.

As to the technical production of carbides,

besides the customary methods well known to chemists, the following processes of production, in which electricity chiefly is used as the eliminating agent, we have found satisfactoy in practice. The metal or base of the carbide is best deposited upon the carbon filament simultaneously with carbon from volatile metallic compounds in the presence of a hydro carbon and hydrogen, or the carbon filaments satu ratedlwith th e easilyreducible compounds poor in oxygen are heated to incandescence in an atmosphere of some hydrocarbon. The metals are reduced by the heat, and at the same time a deposit of carbon is made upon and among the particles of metal, or the metal may be reduced and the carbon deposited in any other convenient way, and thus the reduced metals enriched with carbon. Among the metals suitable for this purpose may be mentioned iron, chromium, and manganese. Of these we preferably usemanganese.

By a proper regulation of the eliminating temperature ,within the preparing apparatus and by a suitable dilution of the mixture of volatile compounds of carbon employed coatings can be produced of various degrees of conductivity.

We claim 1. A filament for electric lamps, composed of a carbon core and a hardly-fusible coating consisting, essentially, of a compound of carbon and manganese, substantially as described.

2. A filament for electric lamps, composed of a carbon core and a coating of carbide of manganese, substantially as described.

In testimony whereof we affix our signatures in presence of two witnesses.

GEORG ER-LWEIN. FRIEDRICH GUSTAV ADOLF HELLER. Witnesses:

HERMAN UBER, MAX WAGNER. 

